Is there a logic to Monty Hall's famous three-door quiz show conundrum, or is it pure chance?

Each contestant hopes to select one of three doors which conceals a prize, makes a choice, is then shown what lies behind one of the others (a booby prize), and is then given the option to swap the original choice with the last remaining door.

On the programme itself, you can hear the views of Howard Huntridge of Fremantle Media, one of the producers of the show worldwide, and of John Kay, who was deluged with mail when he wrote about the Monty Hall problem in the Financial Times.

And when you have finished and decided what you would do, try this variation of the swap problem and see if you can work out why the calculation of probabilities seems so odd...

Imagine two boxes, in which there are two sums of money. All you know is that one of the boxes contains twice what is in the other.

You choose one and open it to find £100. Should you swap?

Objective measurements

Also in the show this week, can you turn our subjective physical feelings into objective measurements?

Our reporter Jim Frank goes to the National Physical Laboratory to find out.

Numbers and ethics

And here is a sum. Divide 2,000 by 5,000. Not too hard in abstract but what if the numbers represent available organs and patients needing a transplant?

Tissue matching used to be all-important. It still matters, but the sum has grown much more complicated.

Find out how it is done and how numbers meet ethics as we talk to a surgeon, a statistician and a patient.

Plus our pick of the most arresting number we have come across this year... and the most "arrestable".

BBC Radio 4's More or Less was broadcast on Thursday, 29 December 2005 at 1500 GMT.